1. Field of the Invention
The present invention relates to a machine tool assembly for machining a family of parts, and in particular, a low cost reconfigurable machine tool that is easily converted to perform a variety of machining operations.
2. Description of the Prior Art
Machine tools for cutting, drilling, tapping, milling or grinding a part from a raw material workpiece are typically dedicated machining lines (DML) or computerized-numerically-controlled (CNC). DMLs are customized hardware lines that can control multiple cutting tools in fixed directions, which are determined at the design stage of the part. They are generally designed to produce a single product and cannot be easily changed.
In DML's, parts that are machined from raw materials are typically made by a series of machining station which require the part to be transferred from one machining station to the next. Each tool performs a different operation on the part, which is then moved on to the next machining station until the machining process is complete. Each of these machining stations is designed and made to process the desired part and generally cannot be easily adapted to perform a different process on another part. Therefore, such a series of machining stations are appropriate for high volume parts, where the costs of the multiple tools and complexity in setting up the series of machining stations can be offset by the high volume of parts produced. However, such systems are not appropriate where a variety of parts are desired so that the additional costs to set up the system cannot be justified.
On the other hand, CNC machines include cutting tools where each machine operates one tool that is operable along several axes of motion and can thus produce a variety of parts. However, not all of these axes of motion are utilized during the production of each individual part. Furthermore, the structure of the CNC machine itself cannot be changed.
By contrast, the object of the present invention is to allow rapid changes in the machine structure and rapid conversion of the machine by relocating its basic building modules. This also allows the performance, on the same basic machine, of a variety of machining processes (such as milling, turning, grinding, etc.) and to machine a variety of part geometries with a small number of controlled axes-of-motion.
The reconfigurable machine of the present invention uses some principles of modular machine tools, but existing modular machine tools are not reconfigurable, nor they can be quickly converted to perform a variety of machining processes as described in the embodiments below. For example, U.S. Pat. No. 4,679,295 describes a modular machine tool for a specific process-machining of parts in a bar. This patent is limited to the design of a machine for machining from a bar.
U.S. Pat. No. 4,218,815 deals with modular transfer machines and is limited to a line consisting of a series of work stations, and does not deal with a single machine. The concept of modularity in this patent is very limited. By contrast the object of the current invention is to implement the concept of spindle-units driven on linear slides as basic modules that can be quickly attached at various locations on reconfigurable support units in order to perform a variety of machining operations.
The advantage of the reconfigurable machine of this invention is that it permits easy reconfiguration of the structure of the machine and its spindle-units to machine a new series of parts belonging to the same part family. It permits reduction in the cost of the machine since it does not have axes-of-motion that are not utilized for the machining of a particular part. The reconfigurable machine rather combines active degrees-of-freedom (driven by motors or other actuators) with passive degrees-of-freedom (manually reconfigured) to achieve "customized flexibility".
Another advantage of the reconfigurable machine of this invention is the possibility of using several tools such that their motion is simultaneously controlled by a computer, thereby combining advantages of DMLs and CNCs. Work stations in dedicated lines can take advantage of using multiple tools that cut the part simultaneously (each group of tools in one direction of motion), thereby achieving high productivity. On the other hand, CNC machines use a single tool that can be manipulated in different directions.
By contrast, the reconfigurable machine of this invention allows the use of several tools that cut simultaneously, thereby increasing the productivity to the level achieved by DMLs. The enhanced productivity achieved with the reconfigurable machine is an important economic benefit. The reconfigurable machine provides the right balance between production speed of DMLs and general flexibility of CNCs.
An additional advantage of the reconfigurable machine of this invention is that it allows the conversion of the machine to do various types of machining operations (i.e., processes), such as drilling, milling, turning, and grinding. On current machine tools all these types of operations cannot be performed on the same machine.
Another cost advantage of the reconfigurable machine is the light structure that reduces the cost associated with heavy metal bases utilized in traditional machines.
It is therefore a primary object of the present invention to fulfill that need by providing a reconfigurable machine tool that is cost effective, highly productive, and is capable of producing desired parts with minimal set up time and costs.
It is another object of the present invention to provide a machine tool that is easily reconfigurable to perform multiple operations in the machining of a family of parts.
It is a further object of the present invention to provide a machine tool that can be easily converted to do various types of machining operations.
It is another object of the present invention to provide a machine tool that has a light structure, yet still provides adequate rigidity in supporting the part so that tight design tolerances are met.
It is yet another object of the present invention to achieve high productivity by using several computer controlled tools to cut or otherwise machine the part simultaneously.